Development of vaccines is a remarkable triumph of medical science. Traditional vaccines consist of protein antigens from pathogens, live attenuated viruses, or killed bacteria. However, the protein antigens are sometimes not efficient in mounting cellular immune responses (e.g. induction of cytotoxic T-lymphocytes, CTLs) which is one of the most sought after components for vaccines. To this end, more recently, DNA vaccination, the administration of antigen encoded DNA, is gaining increasing attention as an emerging therapeutic approach for the treatment of many complex disorders including cancer, infectious disease, and allergies (Ishii, K. J. et al. Nature 2008; 451:725-729, Rice, J. et al. Nat. Rev. Cancer. 2008; 8:108-120). DNA vaccines are capable of inducing both humoral and cellular immune responses and are regarded as potentially safer than their attenuated virus counterparts (Gurunathan, S. et al. Annu. Rev. Immunol. 2000; 18:927-974, Liu, M. A. J. Int. Med. 2003; 253:402-410).
Since the pioneering report by Wolff et al. in 1991 on the use of naked DNA in transfecting muscle cells in vivo (Wolff, J. A. et al. Science 1991; 247:1465-1468), several studies have shown that intramuscular injection of a specific antigen encoded naked plasmid DNA can trigger humoral and cell mediated protective immunity against the antigen (Whalen, R. G. et al. Clin. Immunol Immunopathol. 1995; 75:1-12, Ulmer, J. B. et al. Vaccine 1994; 12:1541-1544, Liu, M. A. et al. Vaccine 1997; 15:909-912, Gurunathan, S. et al. Annu. Rev. Immunol. 2000; 18:1297-1306, Liu, M. A. J. Int. Med. 2003; 253:402-4104-6). However, clinical trials have revealed that the immune response induced by a topical injection of naked DNA is insufficient (Roy, M. J. et al. Vaccine, 2000; 19:764-778, Rosenberg, S. A. et al. Hum. Gene Ther. 2003; 14:709-714). Studies have shown that transfection and subsequent activation of antigen presenting cells (APC) such as dendritic cells (DC) and macrophages are key events in the development of immunity following genetic immunization (Akbari, O. et al. J. Exp. Med. 1999; 189:169-178, Chattergon, M. A. et al. J. Immunol. 1998; 160: 5707-5718). Mountain and co-workers demonstrated that immunization of mice with monocyte-derived dendritic cells transfected with a complex of cationic peptide and a gene encoding tumor associated antigens protected the mice from a lethal challenge with melanoma cells (Irvine, A. S. et al. Nat. Biotechnol. 2000; 18:1273-1278).
Antigen presenting cells such as dendritic cells and macrophages process the antigenic protein through their proteasome complexes into small peptide fragments. These small peptide fragments are then presented to the immune cells (CD8+ and CD4+ T cells) via MHC class I and MHC class II molecules resulting in the induction of cytotoxic T lymphocyte (CTL) and humoral responses (Steinman, R. M. Annu. Rev. Immunol. 1991; 9: 271-296, Banchereau, R. M. and Steinman, R. M. Nature 1998; 392:245-252, Germain, R. N. Cell 1994; 76:287-299, Akbari, O. et al. J. Exp. Med. 1999; 189:169-178, Chattergon, M. A. et al. J. Immunol. 1998; 160:5707-5718, Banchereau, J. and Steinman, R. M. Nature 1998; 392: 245-252). However, antigen presenting cells are hard to transfect. Use of cationic microparticles (Hedley, M. L. et al. Nat. Med. 1998; 4:365-368; Singh, M. et al. Proc. Natl. Acad. Sci. USA 2000; 97:811-816), cationic liposomes (Perrie, Y. et al. Vaccine 2001; 19:3301-3310), and cationic peptide (Irvine, A. S. et al. Nat Biotechnol 2000; 18:1273-1278), etc. have previously been reported for direct transfection of APCs in DNA vaccination. Attempts have been made to increase the potency of immune response through direct transfection of APCs by delivering the antigen encoding DNA via cationic liposomes (Gregoriadis, G. et al. FEBS Lett. 1997; 402:107-110, Klavinskis, L. S. et al. Vaccine 1997; 15: 818-820, Perrie, Y. et al. Vaccine 2001; 19:3301-3310, Hattori, y. et al. Biochem. Biophys. Res. Comm. 2004; 317:992-999). Cationic liposomes owing to their non-toxic and bio-compatible nature offer great advantage over other means of DNA delivery. A greater degree of control can be exercised over the lipid's structure on a molecular level and the products can be highly purified. Use of cationic liposomes does not require any special expertise in handling and preparation techniques. Cationic liposomes can be covalently grafted with receptor specific ligands for accomplishing targeted gene delivery. Such multitude of favorable clinical features are increasingly making cationic liposomes as the non-viral transfection vectors of choice for delivering genes into body cells (Karmali, P. P. and Chaudhuri, A. Med. Res. Rev. 2007; 27: 696-722; Srinivas, R. et al. Chem. Soc. Rev. 2009; 38:3326-3338; U.S. Pat. Nos. 4,897,355 and 4,946,787 (1990); U.S. Pat. No. 5,264,618 (1993); U.S. Pat. No. 5,283,185 (1994); U.S. Pat. No. 5,283,185 (1994); U.S. Pat. No. 5,527,928 (1996); U.S. Pat. No. 5,698,721 (1997); U.S. Pat. Nos. 5,661,018; 5,686,620 and 5,688,958 (1997); U.S. Pat. No. 5,614,503 (1997); U.S. Pat. No. 5,705,693 (1998); U.S. Pat. No. 5,719,131 (1998); U.S. Pat. No. 5,527,928, (1996); U.S. Pat. No. 6,541,649 (2003); U.S. Pat. No. 6,503,945 (2003); U.S. Pat. No. 7,157,439 (2007). In U.S. Pat. No. 7,166,298 (2007), Jessee J. A. and Hearl W. G. disclosed a method for genetic immunization using compositions comprising cationic lipids and antigen encoded DNA.
A promising approach for enhancing the efficacy of DNA vaccination is based on targeting DNA vaccines to APCs via mannose receptor, a 180 kDa multi-domains unique transmembrane receptors expressed on their cell surfaces (Sallusto, F. et al. J. Exp. Med. 1995; 182:389-400). For instance, use of mannan (a ligand for the mannose receptor) coated liposomes for intranasal delivery of HIV-1 DNA vaccine (Toda, S. et al. Immunology 1997; 92:111-117), mannan-coated cationic nanoparticles for topical immunization (Cui, Z. and Mumper, R. J. J. Control. Rel. 2002; 81:173-184) and mannosylated cationic liposomes have been reported for delivering DNA vaccine to APCs (Hattori, Y. et al. Biochem. Biophys. Res. Comm 2004; 317: 992-999, Wijagkanalan, W. et al. J. Control. Rel. 2008; 125:121-130, Lu Y. et al. Biomaterials 2007; 28:3255-3262). Grandjean and coworkers have previously demonstrated that lysine based clusters of mannose mimicking carbocyclic acids such as quinic and shikimic acid are also effective ligands for the mannose receptor of dendritic cells (Grandjean, C. et al. Chem. biochem 2001; 2:747-757, Chenevier, P. et al. Chem. Commun. (comb) 2002; 20:2446-2447). Very recently, Srinivas, R. et al. has shown that cationic amphiphiles with mannose-mimicking quinic and shikimic acid head-groups can target DNA to antigen presenting cells via mannose receptors (Srinivas, R. et al. J. Med. Chem. 2010; 53:1387-1391). This previous work demonstrated that subcutaneous administration of DCs pre-transfected with electrostatic complex of DNA encoded therapeutic MART1 antigen (antigen of human melanoma tumor) and liposomes of cationic amphiphile with shikimic acid head-group provides more tumor protective effect in C57BL/6 mice challenged with aggressive B16F1 melanoma tumor than subcutaneous administration of the corresponding lipoplex of mannosylated cationic glycolipid (Srinivas, R. et al. J. Med. Chem. 2010; 53:1387-1391). However, the efficiencies of dendritic cells transfection by the liposomes prepared from cationic amphiphiles with mannose-mimicking shikimic and quinic acid head-groups were poor (˜3%, Srinivas, R. et al. J. Med. Chem. 2010; 53:1387-1391). Contrastingly, the efficiencies of DC-transfection by the liposomal formulations of the cationic amphiphiles described herein are about 3-4 fold higher (transfection efficiency within the range of 10-12%). Lipids covered in our previously applied patents applications (Indian Patent Application No. 359/DEL/2006; International Patent Application No. PCT/IB 2007/000281, Publication No. WO/2008/001166, Publication date: Mar. 1, 2008) are 3-4 fold less efficient than the presently described lipids in transfecting dendritic cells. In addition, the presently described novel cationic amphiphiles with mannose-mimicking head-groups are efficacious in eliciting both cellular and humoral immune responses in dendritic cell based genetic immunization in mice and are therefore likely to find future applications in the area of DNA vaccination.